Recovery of ammonia and sulfur from waste streams



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Dec. 29, 197.0- G. R. HE-rrlcK ETAL 3,551,102

RECOVERY O:1 AMMONIA AND SULFUR FROMWASTE STREAMS A T TOR/VE VS 3,551,102 RECOVERY OF AMMONIA AND SULFUR FROM WASTE STREAMS George R. Hettick and Donald M. Little, Bartlesville,

Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Filed Feb. 23, 1968, Ser. No. 707,862 Int. Cl. C01b 17/56; C01c 1/00 U.S. Cl. 23--193 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to the recovery of ammonia and sulfur as products from an H3S-NH3-H3O-containing stream such as that obtained on stripping foul water in order to purify same. In accordance with another aspect, this invention relates to a process for the recovery of ammonia from streams also containing CO3, S03, N3 and H30 vapor by absorption with a sulfolane. In accordance with the further aspect, this invention relates to a process for the recovery of NH3 and sulfur as products from H38-NH3-containing streams comprising converting the H38 present in said stream to S03 and free sulfur and treating the off-gas stream obtained therefrom comprising ammonia into CO3, S03 and H30 vapor for extraction either with a sulfolane or a hydrocarbon and recycle of S03 to the initial step.

In many industrial processes, water is utilized in the process for various purposes, and subsequent to its use, the water contains dissolved therein objectionable materials which makes it undesirable to empty directly into streams. Many states have laws regulating the amount of waste which can be dumped and requiring various treatments. In present plant practices, these foul Waters are treated to some extent prior to disposal of these Waters from the industrial plant in order to not pollute streams and other water facilities. Such treatment of foul waters include steam stripping, ue gas stripping, air oxidation, biological treatment, chemical oxidation, extractions, settling, and combinations of these processes, One particular presently preferred method of treating foul waters is to subject them to stripping to remove therefrom various contaminants including NH3 and H38.

The NH3-H38 stream obtained from stripping of foul water contains valuable components which desirably can be recovered. In accordance with the invention a process has now been found wherein streams containing H38 and NH3 such as that obtained upon stripping foul water in order to purify same can be subjected to treatment in a sulfur plant to convert H38 to S03 and sulfur and an olfgas stream containing ammonia and other contaminants is subjected to absorption to recover ammonia therefrom.

Acccordingly, an object of this invention is to provide a process for recovery .of NH3 and sulfur from streams containing H38-NH3.

Another object of this invention is to provide a process United States Patent O ICC for recovering valuable products from gaseous streams stripped from foul processed waters.

Other objects, aspects as well as the several advantages of this invention will be obvious to those skilled in the art upon further study of the specification, drawings and the appended claims.

SUMMARY OF THE INVENTION In accordance with the invention, a process is provided for the recovery of NH3 and sulfur as products from an H38-NH3 containing stream such as that obtained upon stripping foul Water in order to purify same comprising treating the stream in a sulfur plant to convert H38 to S03 and free sulfur, the latter being recovered as product, and treating an off-gas stream comprising NH3, N3, CO3, S03 and H30 vapor in an absorption zone to recover ammonia as product.

In accordance with one embodiment of the invention, the oit-gas obtained from the sulfur plant is contacted with a sulfolane which selectively extracts ammonia and S03 therefrom forming a sulfolane solvent phase rich in ammonia and S03 from which ammonia can later be separated leaving S03 in the sulfolane.

In a preferred embodiment, the sulfolane extraction is carried out in plural stages, the initial stages being at a lower temperature than the later stages wherein ammonia is released and S03 is retained with the sulfolane solvent. The S03 can be stripped from the sulfolane and returned to the sulfur plant for conversion to free sulfur.

In accordance with a further embodiment, the off-gas stream obtained from the sulfur plant is contacted with a hydrocarbon absorption medium, preferably an aromatic hydrocarbon which selectively removes H38 and S03 from the gas stream leaving the gas stream rich in N3 and NH3 which is Washed with Water to recover ammonia.

In accordance with a still further embodiment of the invention, the off-gas obtained from the sulfur plant is contacted with iron oxide to remove the sulfur compounds from the off-gas stream leaving a vent gas containing NH3 and N3 which is washed with water to recover ammonia. The iron oxide can be regenerated by oxidation to form S03 which can be returned to the sulfur plant for production of additional amounts of free sulfur.

DESCRIPTION OF PREFERRED EMBODIMENT A better understanding of the invention will be obtained upon reference to the accompanying schematic drawings which illustrate presently preferred forms of the invention.

FIG. 1 diagrammatically illustrates the stripping of foul water to recover NH3 and H38 therefrom, which stream is subjected to treatment in a sulfur plant to form sulfur and an off-gas obtained therefrom is further treated with sulfolane to recover ammonia as a further product.

FIG. 2 diagrammatically shows another embodiment of the invention wherein foul water is stripped to obtain a stream containing NH3 and H38, Which stream is treated in a sulfur plant to produce sulfur product, and an olf-gas obtained therefrom is treated either with a hydrocarbon to absorb sulfur compounds therefrom or treated with iron oxide to remove the sulfur compounds followed by Water washing of, the oif-gas stream containing N3 and NH3 to recover ammonia as an additional product.

Referring now to FIG. 1, foul water is introduced into stripper 11 by way of line 10. The foul water contains NH3 and H38, as well as other gaseous contaminants. Water vapor, NH3 and H38 are taken overhead from stripper 11 by way of line 12, passed to cooler 13 and introduced into Water separator 14. Foul water which has been stripped of contaminants is removed by `Way of line from stripper 11 and can be passed to steam production if desired. A water stream is also removed from the base of water separator 14 by way of line 16.

A stream comprising NH2 and H2S is taken overhead from separator 14 by way of line 17 and passed either to furnace 18 by way of line 19 or by-pass of said furnace by way of line 20. If desired, al1 of stream 17 can be passed through reactor furnace 18 wherein H2S is oxidized to SO2. Air is introduced into furnace by way of line 21. An eiuent stream removed from reactor 18 comprising SO2 is passed by way of line 22 and line 23 to sulfur converter 24.

Gas stream comprising NH3, H28 and SO2 is passed through a series of sulfur converters, 24 and 25, with sulfur being removed by way of lines 26 and 27, respectively. Effluent from the last converter is passed by way of line 28 to coalescer 29 wherein sulfur is removed by way of line 30 and combined with previous sulfur removal in lines 26 and 27 and removed from the system by way of line 31.

Operating Conditions (Continued):

(44) Absorber:

Table Il, below, is a material balance illustrating the operation of FIG. 1.

TABLE Il FOY Figure 1 Foul Gas Gas to SO2 Gas from Gas feed Sulfur Air to Combustion (typical) Stream water stream generation SO2 genera- Recycle to Asulfur product incinerator products component; (l0) (12) (19 tion (22) gas (50) unlt (23) (3l) (34) (39) H2O Vapor; H2O liquid O2 Sulfolane Total 500, 000 5, 250

Vent gases (42) H2O vapor H2O liquid Sulfolane (41) Suliolaue Ammonia Recycle (45) (46) gas (50) (52) The operation of reactor furnace 18 and converters 24 and is well known in the art and the conditions obtaining therein should be controlled so as to obtain the maximum amount of SO2 and sulfur production from the stream being treated. Illustrative operating conditions of temperature, pressure and ratio of reactant and suitable catalyst are shown in the following Table I, illustrating FIG. 1.

TABLE L FOR FIG. 1

Operating conditions:

(11) Foul water stripper:

Pressure, p.s.i.a 20

Temperature, F. 250 (14) Knock-out keg:

Pressure, p.s.i.a 18

Temperature, F. 120 (18) SO2 generator:

Pressure, p.s.i.a 17

Temperature, F. 1800 (24) and (25) Sulfur zone:

Pressure, p.s.i.a 16

Temperature, F. (bauxite catalyst) 700 (29) Coalescer:

Pressure, p.s.i.a 16

Temperature, F. 300 (33) Incinerator:

Pressure, p.s.i.a 16

Temperature, F. 1700 Absorber:

Pressure, p.s.i.a 17

Top temp., F. 100

Bottom temp, F. 110

An off-gas or waste gas stream is removed from coalescer 29 by way of line 32 and passed to incinerator 33. The Waste gas stream comprises NH3, N2, SO2 sulfur va* por, water vapor, but is substantially free of H2S. Air is introduced into incinerator 33 by way of line 34. Incinerator 33 is operated ordinarily at a temperature in the range of 1500 to 1800o F. An effluent stream is removed from the incinerator which comprises NH3, N2, SO2, CO2 and H2O vapor by way of line 35, passed through stack 36, and then line 37, into compressor 38. The etiiuent removed from compressor 38 in line 39 is passed to absorber 40 wherein the gas stream is contacted with lean sulfolane introduced into an upper portion of absorber 40 by way of line 41. An overhead stream comprising unabsorbed N2 and CO2 is removed from absorber 40 by way of line 42. Absorber 40 is operated at a temperature of about F.

A rich sulfolane stream containing NH3, SO2 and H2O is removed from the base of absorber 40 by way of line 43 and introduced into an intermediate portion of absorber 44. Additional lean sulfolane is introduced into absorber 44 by way of line 45. Absorber 44 is operated at a temperature of about F. An overhead stream comprising NH3 product is removed from absorber 44 by way of line 46.

The rich sulfolane liquid removed from the bottom of absorber 44 by way of line 47 is passed to SO2 stripper 48 wherefrom SO2 is removed overhead by way of line 49 and can be recycled to line 23 by way of line 50 for conversion to sulfur in the sulfur plant as previously described. Stripper 48 is operated at a temperature of about F. The bottoms stream from stripper 48 in line 51 comprising water and sulfolane is passed to the sulfolane regenerator 53 by line 52 to strip out water overhead by line 54 and return lean sulfolane substantially freed of water to line 51 by way of line 55. Sulfolane regenerator the sulfur. An eluent stream is removed from unit 8.2 53 is operated at a temperature of about 220 F. and by Way of line 98 which eluent comprises N2, CO2, steam is introduced into the base of the regenerator by NH3 and H2O which is passed to absorber 86. If desired, way of line 56. this eluent stream either all or in part if it contains Referring now to FIG. 2, foul water is introduced by SO2 can be passed by way of line 99 for further processway of line into stripper 61. The foul Water contains ing as absorption with sulfolane as set forth in connection ammonia, H2S, CO2 and other contaminants. A gas with FIG. l.

stream comprising ammonia, H2S, CO2 is taken overhead After the iron oxide has been used for some time, it by way of line 62 and a substantially purified Water stream may be regenerated for further use by treating with air removed as bottoms by way of line 63 from stripper 61. 10 introduced by line 1010 into regeneration unit 101. An The gas stream is cooled and passed to separator 64 emu/ent stream is removed from regeneration unit 10-1 wherein water is removed as bottoms by way of line 65 lby Way of line 102 and returned either to the influent or and an overhead gas stream of NH3, H28, CO2 and water eluent of SO2 conversion unit 68 as desired by Way of vapor is removed by line66. line 96 or 103. This stream contains SO2 and other sulfur In accordance with one operation of this gas stream, 15 material. all or a part is passed by way of line 67 to SO2 conversion Table III illustrates the operation of FIG. 2. unit 68, wherein gas stream is contacted with air or oxy- TABLE IH gen introduced by way of line 69 to oxidize HZS to SO2. Operating conditions, 1f desired, a portion of the gaseous stream in line 66 can (61) Foul Water Stripper: by-pass SO2 conversion unit 68 by Way of line 70. An 20 Pressure p s i a 20 eiuent stream containing SO2 is removed from unit 68 by Temperture o 1 250 way of line 71 and then passed by way of line 72 to the (64) Knockmlt 126g: sulfur plant 73. The sulfur plant is operated in the same Pressure p s'i a 18 manner as set forth above in connection with FIG. 1. Temperature o F 120 Sulfur product is removed from plant 73 by way of line 25 (68) SO2 generator:

74. If desired, a portion of the sulfur removed from plant Pressure p si a' 17 73 can be returned to SO2 unit 68 by way of line 75 to- Temperature yF 1800 gether with air or oxygen introduced by way of line 76. (73) Sulfur Zone? An off-gas Stream Comprising NH3, H28, N2, SO2, H2O, pressure, p sm 16 sulrur Vapor and CO2 1s removed from plant 73 by way 30 Temperature, o E (bauxite catalyst) 700 of l1ne 77, cooled to remove water by cooler 78, passed (81) Absorber: to compressor 79, and then passed through line to Pressure p s i a 17 either absorber 81 or iron oxide converter 82. TOP tempo F 100 Off-gas in this embodiment is introduced into absorber Bottom ternp- L F- 110 81 by way of line 83. Within absorber `81 the off-gas is 35 (94) Stripper: contacted with a hydrocarbon solvent, preferably an Pressure p sia' 16 aromatic hydrocarbon solvent such as benzene, by way Top temp. o F 220 of line 84. A vent gas stream is removed overhead from Bottom ternp s F" 240 absorber 81 by Way of line 85, which stream comprises (86) Absorber. CO2, N2, NH3 and H2O and is passed to a secondabsorber 40 Pressure I'LS i a 20 86. In absorber 86 water is introduced into upper portion Top ml {,F' T:I: 100 by way of line 87 to remove NH3 from the gaseous stream Bottom telnp u F 110 by way of line 88. The water stream containing ammonia (89) Stripper: is passed to stripper 89 wherein the ammonia is taken Pressure P S i a 18 overhead by way of line 90 and water is removed as 45 Top tempu E 200 bottoms and returned by way of line 87 to absorber 86, Bottom temp F- 215 following cooling in cooler 91. A stream comprising N2 (82) Treating Zone; and CO2 is removed overhead from absorber 86 by way Pressure, p.s.i.a 2O of line 92 for further processing as desired. 50 Temperature, F. 100

Referring again to absorber 81, the hydrocarbon sol- (101) Regeneration zone: vent absorbs the sulfur compounds including H2S, free Pressure, p.S.i.a 2O sulfur and SO2, and is removed from the base of ab- Temperature, F- 80 SOfbl 81 by Way 0f line 93 and Passed t0 Stripper 94. Table IV, below, is a material balance illustrating the The sulfur compounds in the solvent are removed over- 55 operation of F1G 2,

TABLE IV Feed to Foul sulfur Sulfur Water ReCYCle 13121111 Product Olgas Benzene O-gns Off-gas Ammonia stream component (60) (102) (72) (74) (77) (s4) (85) (92) (90) GUZBHQ Total 500, 000 14, 520 725 14, 780 1, 000, 000, 14, 680 11, 770 1, 380

head from stripper 94 by Way of line 9S and returned by 70 Sucient solvent is used in the absorption systems to way of line 96 to the SO2 conversion unit. attain the desired recovery at minimum costs, and can be If desired, all or a portion of the off-gas in line 80 easily established by one skilled in the absorption art.

can be passed by way of line 97 to iron oxide treatment Examples of aromatic hydrocarbon solvents which can in unit 82. In unit 82 the iron oxide reacts with the hybe used in our process include such as benzene, toluene,

drogen sullide and other sulfur compounds and absorbs 75 xylenes, ethyl benzene, propyl benzene, and the like, and

admixtures thereof. Other hydrocarbon solvents include cycle oils such as produced by cracking hydrocarbons and aromatic extracts thereof.

The sulfolane solvents of the invention comprise tetrahydrothiophene-l,l-dioxide having the formula R, R-l l-R wherein each R is selected from hydrogen, methyl, and ethyl radicals, and R is selected from hydrogen and alkoxy radicals having 1-5 carbon atoms. The simplest of these is sulfolane, C4H3SO'2.

Other known liquid solvents which can be used for removal of sulfur dioxide from gases include such as acetone, formic acid, and the like.

We claim:

1. A process for the separation and recovery of NH3 from a gaseous stream containing NH3, CO2, SO2, N2, H2S and H2O vapor which comprises contacting said stream in an absorption zone with a sulfolane as an absorbent under absorption conditions to selectively extract NH3 and SO2 therefrom and form a sulfolane solvent phase rich in NH3 and SO2 and a gaseous stream containing unabsorbed materials comprising CO2, N2, H2S and some NH3 and SO2, and separating and recovering NH3 from said sulfolane solvent phase by increasing the temperature of said solvent phase to remove NH3 therefrom and leaving SO2 in the sulfolane solvent phase.

2. A process according to claim 1 wherein said absorption is carried out in plural stages at different temperatures wherein the first stage is at a lower temperature than later stages so as to selectively absorb NH3 and SO2 from said gaseous stream with the solvent in the first stage and separating and removing NH3 from the solvent in the latter stages which are operated at a higher temperature, leaving SO2 in the solvent phase, and desorbing SO2 from the solvent phase.

3. A proctss according to claim 1 for the recovery of ammonia and sulfur as products from an H2S-NH3-H2O- containing stream obtained upon stripping foul Water in order to purify same which comprises:

(a) passing said stream to a sulphur plant and oxidizing H2S in said stream to form SO2 and reacting unreacted H2S with SO2 to produce free sulfur and water and removing free sulfur thus produced as product from the process,

(b) obtaining from said sulfur plant an off-gas stream comprising NH3, N2, CO2, SO2 and H2O vapor,

(c) passing said stream obtained in step (b) to a solvent extraction zone wherein said stream is contacted with a sulfolane under absorption conditions to selectively absorb NH3 and SO2 therefrom and form a sulfolane solvent phase rich in NH3 and SO2 and leaving an unabsorbed stream comprising N2 and CO2,

(d) desorbing absorbed ammonia from the solvent phase by increasing the temperature and leaving SO2 in said sulfolane solvent phase and recovering ammonia as product,

(e) further increasing the temperature of said sulfolane solvent phase reduced in NH3 content to desorb SO2 therefrom, and

(f) recycling desorbed SO2 to said sulfur plant for the production of additional amounts of free sulfur as product.

4. A process according to claim 3 wherein said absorption zone comprises a two-stage absorption operated at different temperatures, the first stage being at a lower temperature than the second stage, whereby NH3 and SO2 are absorbed in the first stage and ammonia is desorbed and released overhead from the solfolane in the second higher temperature stage, and further wherein SO2 is desorbed from the sulfolane in a stripping zone.

5. A process according to claim 4 wherein the bottoms stream comprising water and sulfolane is removed from said stripping zone and is subjected to further stripping for removal of Water and return of substantially dry sulfolane as absorbent to the process for recovery of additional amounts of ammonia and SO2 for reuse in the process.

6. A process according to claim 4 wherein said first stage is operated at about 100 F. and about atmospheric pressure and said second stage is operated at least about 50 higher than said first stage and at about atmospheric pressure.

7. A process for the recovery of sulfur and NH3 from a gaseous H2S-NH3-containing stream obtained upon stripping foul water in order to purify same which coniprises:

(a) passing said gaseous stream through a sulfur plant wherein H28 is oxidized to SO2 and unreacted H25 is reacted with SO2 to form free sulfur which is removed as product,

(b) producing an off-gas stream in step (a) comprising NH3, N2, CO2, unreacted H2S, sulfur vapor, and SO2.

(c) passing said o-gas stream to an absorption zone wherein said stream is contacted with a hydrocarbon solvent that selectively removes H2S and SO2 therefrom and leaves a gas stream rich in N2 and NH3 and which latter gas stream is Washed with water to remove ammonia as product, and

(d) recovering H2S and SO2 by stripping same from said solvent removed in step (c) and returning same to step (a).

8. A process according to claim 7 wherein step (c) is an absorption zone employing an aromatic hydrocarbon as a solvent that selectively absorbs H2S and SO2 therefrom and leaves a gas stream rich in N2 and NH3 which is washed with water to remove NH3 as product therefrom and step (d) is a desorption step wherein H28 and SO2 are desorbed from the aromatic hydrocarbon and returned to step (a).

9. A process according to claim 7 wherein step (c) employs iron oxide to remove sulfur compounds and leave a vent gas which is washed with water to recover ammonia as product therefrom, and (d), the iron oxide is regenerated by oxidation to form SO2 which is returned to step (a).

References Cited UNITED STATES PATENTS 1,880,741 10/1932 Boswell 23-226 2,992,076 7/1961 Thompson et al. 23-225 3,050,370 8/1962 Urban et al. 23-226 3,338,664 `8/1967 Bally et al. 23--2 OSCAR R. VERTIZ, Primary Examiner H. S. MILLER, Assistant Examiner U.S. Cl. X.R. 

